Arc length control

ABSTRACT

In automatic arc welding systems where a consumable electrode wire is continuously fed to a weld zone through a holder, the holder serving to provide an electric current path to the weld electrode, the arc length and position is maintained by sensing means that sense preselected spaced areas along the arc path preferably near its extremities and means responsive to one of the sensing means failure to sense the presence of the arc appropriately alters one or more of the arc parameters to restore it to the view of the sensor.

United States Patent inventor Robert E. Pollock Hilliard, Ohio Appl. No.835,327 Filed June 23, 1969 Patented Aug. 31, 1971 Assignee The BattelleDevelopment Corporation Columbus, Ohio I ARC LENGTH CONTROL 16 Claims, 6Drawing Figs.

u.s. Cl 219/130, 219/131, 219/137 Int. Cl B23k 9/00 Field of Search219/130, 131, 131 F, 137

[56] References Cited UNITED STATES PATENTS 2,994,763 8/1961 Schultz....219/123 3,209,121 9/1965 Manz 219/130 3,233,076 2/1966 Vilkas 219/131Primary Examiner.l. V. Truhe Assistant Exa minerC. L. Albritton'Attomey-Gray, Mase and Dunson MOTOR CONTROL PHOTOCELL AMPLIFIERPATENTED M1831 I97! 3.602687 sum 1 0r 3 MOTOR CONTROL PHOTOCELLAMPLIFIER PATENTE[IAUB3HQ71 3.602687 I sum 2m 3' MO OR CONTROL PHOTOCELLAMPLIFIER PATENTEU M1831 I97! 3502- 687 sum 3 [IF 3 PHOTOCELL AMPLIFIERR2 RI PC? Pc 6| PCI P62 '11- 3 uov AC CR2 cns CR4 79 an, e3

{95 cm-u cr z z-u q FUSE 4 k I J I J "E TER4-| ER4-2 cR3-|"ER3-2 Jam/9|L7 f C TORCH suns omve MOTOR AND CONTROL 35 l c 2 MOTOR CONTROL 191' I ll I TO MOTOR CONTROLLING WIRE FEED SPEED OR ARC LENGTH CONTROLBACKGROUND This invention relates to improvements in automaticconsumable elecu'ode welding systems and relates in particular to newand novel sensing means that sense the length of the are fed through aholder onto or into a weld zone usually consisting of abutting plates(which may or may not be machined to form a depression to receive theweld metal) it is generally possible to adjust the amperage, voltage,electrode feed rate, and speed at which the holder (and wire) pass overthe weld zone so that the electrode wire is consumed at a regular rateand assuming the workpieces to be perfectly flat and smooth so that thespacing between the electrode current path (usually from the holder) andthe workpiece is uniform the arc will be stable and uniform and adesirable uniform weld will be obtained. Unfortunately the assumption onwhich the afore mentioned statement is made is seldom the case. Inactuality it is impractical in production runs to obtain perfectly flatworkpieces both from a standpoint of desired welded shapes and the factthat even flat shapes are seldom perfectly flat. Also the heat of anywelding operation can'cause the weld pieces to warp.

Where the distance between the workpiece and the electrode contact isreduced or increased the length of the arc remains the same because thewelding machine automatically maintains a constant voltage byappropriately increasing or decreasing the amperage. The effect is tolengthen or shorten the length of the electrode from its point ofcurrent contact reducing or increasing current resistance and raising orlowering the amperage. An increased amperage effects too great apenetration of the weld area while a decreased amperage effects toolittle penetration of the weld area. The result is that the weld isuneven unless an arc adjustment or control system is employed.

. Prior known are control systems generally consist of one or moresensing devices trained on the arc and designed to detect variations inthe intensity of the arc. Means responsive to these devices alter theare parameters in a manner to correct the deviations. The difficultiesexperienced with devices of this type are that the changes in arcintensity are too subtle for accurate detection; the arc varies inintensity in accordance withthe area being observed and it is difficultto maintain the sensing device trained on a specific portion of an arcparticularly when the arc is moving; and the measurable changes in arclight intensity are difficult to translate into corrective measuresrapidly enough to avoid undesirably uneven weld deposits.

1 have now found that a more accurate measurement of arc changes is thearc position rather than its intensity and that such changes may betranslated into corrective measures far more rapidly and effectivelythan has been possibly with prior known devices. In my method andapparatus are sensors watch preselected spaced areas along he arc itselfand when one of the sensors fails to detect the presence of the arcimmediate corrective measures prevent uneven welding to an extent notheretofore possible.

I have further found that my apparatus and method may be advantageouslyemployed to control are penetration in narrow gap welding procedures. Inthis type of welding plates or workpieces are positioned adjacent oneanother but a space or gap is left therebetween. The consumableelectrode is continuously passed into the gap where the arc effectsfusion and welding. Variations particularly in gap width causes the arcto either overpenetrate or underpenetrate the gap effecting unevenwelding.

1 direct my arc length sensing means into the gap to define apreselected arc position (penetration) and cause the sensing means toremain .spaced from the gap while traveling over it. By this procedurewhen one of the sensing means fails to detect the presence of the are itmeans that the am has over or under penetrated. Corrective measures areimmediate.

In a preferred embodiment of my invention an arc-corrective measureconsists of raising or lowering. the electrode holder which in effectincreases or decreases the electric current path to the electrode andincreases or decreases arc penetration.

Other effective means of controlling arc penetration include varying thespeed at which the electrode or electrode holder passes over the weldzone and varying the consumable electrode feed rate.

THE DRAWINGS FIG. 1 is a side elevation view in accordance with thecontrol.

FIG. 2 is an enlarged fragmented front view of the arc of the apparatusof FIG. 1 and immediately surrounding structures.

FIG. 3 is an enlarged fragmented side view partially in cross section ofone of the optics of the apparatus of FIG. 1.

FIG. 4 is a side elevation view of an apparatus constructed inaccordance with the present invention for narrow gap welding arccontrol.

FIG. 5 is an enlarged fragmented front view of the arc of the apparatusof FIG. 4 and immediately surrounding structures.

FIG. 6 is an illustrative circuit diagram for controlling the apparatusof FIG. 4. I

In the apparatus of FIG. 1 a vertically moveable electrode holderassembly 10 mounted to a horizontally moveable frame 12 is positioned toguide a continuously advancing wire electrode 16 onto a workpiece 14. Anopposing electrical potential (AC or DC) is established betweenworkpiece l4 and electrode 16 to effect arc 18 by means of anappropriate electrical connection 20 to workpiece 14 and conduit 22having an electrical conducting path leading to a metal tube 23 (usuallyconstructed of copper) mounted in the head portion 26 of the electrodeholder 28. Tube 23 has sliding electrical contact with the consumablewire electrode 16.

The consumable wire electrode 16 is fed continuously to the holderassembly 10 and are 18 (where it is consumed) from wire reel 30 by meansof drive rollers 32.

Electrode holder assembly 10 is composed of a carriage 34 that isslidably attached to frame 12 through vertically spaced guide rods 24formed'in (or attached to) frame 12 which extend through and dovetailwith appropriate slots (not shown) in carriage 34.

Electrode holder 28 is attached to a carriage 34 by an appropriatelybolted flange plate 36. Vertical movement or position of carriage 34 andthus holder 28 is controlled by a reversible drive motor 38 bolted toframe 12 and positioned above carriage 34. Motor 38 is positioned todrive a vertically extending drive screw or worm 40 which extendsthrough an appropriately threaded bore (not shown) in carriage 34. Thus,assembly 10 is raised or lowered in accordance with the direction andspeed of rotation of the drive screw 40 by motor 38.

As in conventional continuous and automatic welding of this type thespeed at which rollers 32 advance wire 16 to the arc 18 is synchronizedwith the current and other welding parameters to maintain the arc atpreselected intensity or length while being continuously consumed. Aconstant potential welding machine provides a constant voltageregardless of fluctuations in current flow. If the spacing between theworkpiece and the tube 23 (electrical contract point) remains constantduring horizontal travel of the overall assembly the weld deposit isconsistent and no need for the present invention exists. However, inanswer to the practical problems arising during automatic weldingprocedure wherein the space between of an apparatus constructed presentinvention for proximity arc the workpiece 14 and contact 23 varies (seeFIG. 1) I provide sensing means 42 which through proper response bymotor 38 maintains a relatively consistent and uniform weld bead.

In the embodiment of FIG. 1 sensing means 42 is attached to carriage 34so as to vertically (as well as horizontally) follow carriage 34 (andthus holder assembly by means of depending arm 44. Sensing means 42itself consists of optics 46 and 48 (light guide tubes) attached to asupport plate 50 and oriented to receive and guide arc light from twospaced points 46a and 48a along the length of are 18 preferably neareach end of the arc. Such orientation may, of course, be preselected ormay be established after the arc is struck. A filter or optic 52 may bepositioned in front of optic or light guide tubes 46 and 48. Light fromoptics 46 and 48 is conducted to photoelectric cells 56 and 58respectively which, through an appropriate photo cell amplifier 60,maintains electric current flow disposed hold relays or switches open ina motor control system 62 which, if closed, would cause motor 38 torotate drive screw 40 in a manner to lower or raise assembly 10respectively. 7

Optics 46 and 48 are identical, a representative cross-sectional viewbeing shown by FIG. 3. In this preferred. sensing device masking plates47 and 49 mounted in opposing ends of a metal tube 51 are formed withaligned slits 55 and 57. Tube 51 attached to carriage 50 is aligned sothat the area 460 or 480 is clearly visible through slit 57 by way ofslit 55. To be sure the visible light in slit 57 is detected by theappropriate photo cell 56 or 58 a bundle of fiber optics 59 ispositioned and split so that many of the fiber ends cover the open endof slit 57 and convey all possible light coming through the slit to theappropriate photocell at the terminal end of the fibers. This type ofoptic has proved to be particularly useful for sensing a very small areaalong an arc and consequently is a preferred embodiment of the presentinvention.

In operation, if a stable arc 18 has been established and the overallapparatus is moving in the direction of the arrow so that a weld bead isbeing deposited on workpiece 14 (abutting joint, etc.) as long as cells56 and 58 see arc light the relays in motor control 62 will not closeand the assembly 10 will not raise or lower. Should the distance betweenthe, holder and the workpiece change electrode wire 16 will continue toadvance and maintain the arc length independently of the holder,however, the electrical characteristics of the arc will change due tothe fact the current path or the distance between contact 23 andworkpiece 14 or the length of the tip of the electrode 64 extending fromhead 26 will change thus changing the amperage and the degree of weldmetal penetration.

For example, should the space between contact 23 and workpiece l4diminish the length of tip 64 would be reduced,

reducing the current path and electrical resistance offered by tip 64,increasing the amperage. In the present apparatus and process, however,cell 58 would immediately fail to sense light, interrupting the currentto control 62 that holds open the relay that causes motor 38 to rotatedrive 40 in a direction to raise assembly 10 to where the spacingbetween contact 23 and workpiece 14 is reestablished and cell 58 isagain energized to open the relay energizing the motor whereupon theprescribed length of tip 64 and the prescribed amperage will bereestablished.

Should the space between contact 23 and workpiece 14 v become too great,cell 56 would fail to detect light cutting the current that holds therelay open that causes motor 38 to lower assembly 10. Holder 28 thenlowers until the preselected distance between contact 23 and workpiece14 is reestablished or where cell 56 detects point 46a to open the relaythat energizes motor 38. By reducing the length of tip 64 the amperageincreases to its original setting.

Such positioning of holder 28 is sufficiently rapid and continuous tomaintain a stable arc of consistent length that provides a surprisinglyuniform weld deposit although the surfaces of the workpieces arerelatively uneven.

Turning now to the embodiment of FIGS. 4 and 5 wherein the apparatus ofthe present invention is disposed to control weld penetration duringcontinuous and automatic narrow gap welding between spaced plates. Inthis type of welding an arc is established between the plates. Aconsumable wire electrode is continuously fed into a gap between theplates while being advanced horizontally. An electrical potentialestablished between both plates and the electrode effects an essentiallyelongated flame which causes melting of the adjacent plate surfaces andin combination with the metal of the consumable wire electrode creates aweld. The established arc is generally of less length than the gage ofthe plates and is prepositioned within the gap by proper control of theparameters of amperage, voltage, electrode feed rate, etc. For example,it is frequently desired to regulate these parameters so that the arc iscentrally positioned between the workpiece plates (see FIG. 5).

Irregularities, particularly in gap spacing (i.e., a wider gap at oneend than at the other), frequently result in overpenetration (are toolow) or underpenetration (arc too high) in the space between the platesleading to uneven weld deposits and an inferior product. 7

In the application of the present process and apparatus to narrow gapwelding we mount the sensor means 42' on a separate carriage 50' whichis mounted on wheels 51 to permit horizontal travel with frame member12' but which is slideably engaged to the frame by guide rods 24' whichextend through and slideably engage slots within carriage 50' so thatthe carriage and sensing means do not move vertically with carriage. 34'but are vertically spaced in respect to the gap or workpieces. Otherwisethe apparatus of FIGS. 4 and 5 may be substantially identical to that ofFIGS. 1 and 3.

In operation, however, there are significant differences between theembodiments of FIGS. 4 and 5 and those of FIGS. 1 and'2. Optics 46' and48 are trained within the gap to the location desired and to observe twospaced points within the desired are (preferably defining the length ofthe are or flame). Once the arc is established consumable wire electrode16' is, of course, fed into the gap through holder 28' at a ratedetermined to maintain the arc withinthe desired limits duringhorizontal travel in the direction of the arrow. However, where the gapwidth varies and arc penetration becomes too great (too low in the gap)cell 56 will fail to detect light. In. this event the electrical currentneeded to keep the relay .of control 62' open which causes motor'38' torotate screw 40' in a manner to raise head 28' is cut off. Thus the headis raised until cell 56' again detects light to reestablish the relayopening current. Raising the head lengthens the current flow path byextending the length of tip 64', increasing current resistance, loweringamperage, and decreasing the propensity of the arc to overpenetrate thegap since greater amperage is required to maintain the are at alowerdepth. Where cell 58' fails to detect light there is insufficientarc penetration and the relay closes to cause motor 38' and drive screw40' to lower head 28 shortening tip 64 to reduce current resistance andto raise the amperage causing the are 18' to effect greater penetration.Thus, arc 18 is maintained within the length defined by optics 46' and48'.

In still another embodiment of the present invention, further improvedconsistency of welding utilizing the apparatus of FIGS. 4 and 5 iseffected by synchronizing the vertical positioning of head 28' withincreased horizontal speed of the apparatus. This is most easilydescribed in conjunction with FIG. 4 by an illustrative horizontaldriving means that is essentially identical to the electrode holdervertically positioning means. The illustrative horizontal driving meansconsists of a horizontally positioned anchored reversible motor 39 thatis disposed to rotate a worm or screw drive 41 that projects throughappropriately threaded orifices of frame 12. Motor 39 may be of a typecapable of three speeds-the middle speed being gaged for normal weldinginvolving perfectly spaced plates, a fast speed being slightly greaterthan normal, and a slow speed being slightly less than normal. Cell 56'in this embodiment may generate two currents-one which maintains a relayopen in the motor control which energizes motor 38' to lower holder ifclosed and one which maintains a relay open which energizes motor 39 togo from normal speed to fast speed when closed. Thus, if there isoverpenetration and cell 56' fails to see light not only is holder 28'raised to reduce the amperage to flame 18 but the apparatus decreasesits speed in the direction of the arrow so that the arc plays on theweld pool to some extent which tends to reduce overpenetration. 1

Conversely, failure of cell 58 to view light will cause relays to closethat will shift motor 39 into high speed and lower holder 28' causingare 18' to lead the molten pool and lowering the amperage both of whichtend to increase arc penetration.

A still'further embodiment of the present invention relates to theelectrode drive system. Where there is overpenetration a-decreased speedof rollers 32, feeding roll 16 to the arc at a slower rate, will tend toreduce arc penetration whereas an increased weld wire feed rate willtend to increase are penetration. Thus, relay contacts may be employedin conjunction with cells 56' and 58' in the manner described with thehorizontal drive and vertical electrode positioner either in combinationwith these systems or alone.

FIG. 6 of the drawings is a schematic circuit diagram of the arc lengthcontrol of the apparatus of FIGS. 4 and 5 as modified to includeadjustment of horizontal travel speed or electrode wire feed rate.

in this diagram energization of photocells 56' (PCI) and 58' (PC2) keeprelay coils CR1 and CR2 energized through leads 61, 63, 65 and 67 to thephotocell amplifiers and leads 69 and 71 from the amplifier. Energizedcoil CR1 maintains contact CR1-l open and CR1-2 closed while energizedcoil CR2 maintains contact CR2-1 open and CR2-2 closed. Thus, the torchslide drive and motor control remains deenergized since contacts CR1 andCR2 remain open so long as cells 56' and 58' sense are light.

If cell 56 fails to detect light coil CR1 is deenergized (due to lack ofcurrent in lead 71) closing contact CR1-l and opening contact CR1-2.Coil CR2, however remains energized through leads 69 and 75 throughcontacts CR1-l, CR2-2, the torch slide drive motor and control and leads77 and 79. Consequently the torch slide drive motor and control areenergized to raise head 28'.

When cell 56' again detects light, current flow in lead 71 will againcreate the necessary flux in coil CR1 to open contact CR1-1 and closeCR1-2 deenergizing the torch slide drive and control motor. 7

So long as relay coils CR3 and CR4 are deenergized contacts CR3-l andCR4-l remain open and CR3-2 and CR4-2 remain closed so that the motorcontrolling shifts in the wire feed speed or travel speed remainsdeenergized. However, where cell 56' fails to detect are light andcontact CR1-1 is closed in the manner described above coil CR4 isenergized to render a flux through leads 69, 79, 77 and 83 and lead 75,contacts CR1-l and CR2-2 and lead 85 to shift the wire or travel speedmotor through leads 87 and 89 to decrease the speed of the motor.

In a like manner when cell 58 (PC2) fails to sense light coil CR2 isdeenergized since lead 69 fails to carry a current, however coil CRlremains energized through leads 71 and 75 (via contacts CR2-l and CR1-2,the slide motor drive, leads 77 and 79). Thus the slide motor isenergized to lower holder 28'.

Simultaneously coil CR3 is energized through leads 81 and 83 whilecurrent is blocked to coil CR4 by contact CR1-l so that the wire feed ortravel speed motor is shifted to high gear (2) through contact CR3-1 andlead 91 and contact CR4-2 through leads 93 and 89.

The connections 1, C, and 2 of the motor controlling wire feed speed ortravel speed lead to a reversible motor that drives a potentiometercontact through which the actual motor is driven. When C is connected to1 (through contacts CR4-1 and CR3-2) the polarity of the drivenreversible motor is such to drive the potentiometer in a direction toreduce the voltage supply to the motor controlling the wire or travelspeed. Where C is connected to 2 leads 89 and 91 (through contactsCR3-l. and CR4-2) the polarity of the potentiometer motor drive isreversed to drive the potentiometer contact in a direction to increasethe wire feed or travel speed.

it will be obvious to those skilled in the artthat eitherthe weld wirefeed rate or the horizontal speed may be employed alone to bring the are18' back into the preselected penetration position between plates 14'and 14 or any combination of these systems may be so employed.

lt will also be obvious to those skilled in the metal joining art thatthe above described apparatus may bemodified to a considerable extentwithout deviation from the scope of the invention. For example, sensingmeans 42 and 42' may be any sensing device capable of detecting arclight within a relatively restricted vertical space. For example, suchsensors may be composed of photoelectric cells mounted behindhorizontally extending vertical slits disposed to mask all but a verylimited vertical area of the arc. Or such cells may be aligned withvarious optic systems disposed to amplify only preselected areas of thearc.

A significant feature of the method and apparatus of the presentinvention relates to the fact that the sensing means of the presentinvention is disposed to observe two spaced vertical points along theare or along a desired path of the are rather than determine theintensity of the are as in prior art systems of this type. By such'arclength and position control I am able to effect a rapid response andmaintain a uniform weld deposit and structure in the face of theinevitable deviations that are difficult to control with other systems.

In practicing the present invention 1 used a Linde OM48 side beamcarriage and track. The welding torch (or holder) was an Airco weldingtorch (Model A H 20,) mounted to a carriage such as carriage 34 which,in turn, was mounted to the side beam carriage on slide rods such asthose described in conjunction with FIG. 1. Motor 38 was a reversiblesl0sgn motor (Type SS-150P2 mfg. by Superior Electric Motor Co.). Theelectrode wire drive and welding controls were Airco Wire Feed Drive andWeld Controls (Model No. AH F-N). The constant-voltage welding machinewas a Linde SW 750 (for other satisfactory constant voltage weldingmachines see the descriptions of U.S. Pat. Nos. 2,5 32,410 and2,532,411).

Optics 46 and 48 consisted of structures such as depicted by FIG. 3. Theslots 55 and 57 were approximately 0.010 inch X 0.50 inch. Tube 53 wasapproximately 3 inches long. The fiber optic bundles were AmericanOptical Co. Light pipes."

photocells 56 and 58 were cadmium-selenium Clairex Mfg. Co. No. CL904L.

The electrode wire was 0.035 inch gage mild steel.

When the device was used for penetration control carriage 50 was removedfrom arm 44 and attached to frame 12 while appropriately directing thesight of optics 46 and 48 into the narrow gap. M

Control of the speed of motor 39 (which in actual practice drive frame12 along a conventional sidearm track) was controlled through a slow-snyreversible motor-driven potentiometer. In other words when cell 56'failed to detect light it caused a relay to close that drove thepotentiometer motor rather than motor 39 directly.

PROXlMlTY CONTROL The are sensor was set up to control the proximity ofthe weld torch above the surface of a plate (FIGS. 1 and 2). A dialmicrometer was attached to the weld torch to indicate movement of theweld torch with respect to the surface of the plate on which the weldbeads were deposited. The plate was set up with a rise of one-half inchin 24 inches. Then during deposition of the 24 inch long weld bead thearc sensor had to command the slide drive motor to raise the weld torchone-half inch to maintain the weld torch at a constant height of onehalfinch above the surface of the plate. Four weld beads 24 inches long weremade to check sensitivity of the arc sensor. The maximum deviation was$0.015 inch, however the majority of the time it was 10.010 inch.

. 7 PENETa/iiioii CONTROL The are sensor was then set up for narrow gap"welding in the manner of FIGS. 4 and 5. Mild steel plates one-fourthinch thick were positioned for square butt joints with a varying gapwidth of one-sixteenthto one-eighth inch. Contact-tube-to work distanceand travel speed control (as set forth in conjunction with FIGS. 4 and5) gave better results than contacttube-to-work distance alone. The dualcontrol gave better results providing adequate fill in the wide gapareas of the weld joint.

When welding 3/ l6-inch-thick mild steel plates using a square buttjoint design with a varying gap width of l/ l 6 to D- inch glass-fibertape was placed on the root side of the weld joint. Good welds with goodroot penetration and contour were obtained. Similar results wereobtained when the gap width was increased to one-sixteenth inch tothree-sixteenth inch.

I claim:

1. A method for controlling the vertical position of an arc duringcontinuous arc welding comprising the steps of:

a. establishing an are between an electrode and adjacent workpieces andconducting said are along a path to effect fusion and welding of saidadjacent workpieces; positioning at least two aligned vertically spacedsensing means to detect preselected spaced areas along the length ofsaid arc during its travel along said path, said sensing means beingdisposed to individually indicate when they fail to detect the existenceof said arc; and

c. changing at least one are influencing parameter to bring said areback into the area of detection of each of said sensing means wheneverat least one of said sensing means fails to detect the existence of saidarc.

2. The method of claim 1 wherein said influencing parameter consists ofchanging the electric current amperage supplied to said arc.-

3. The method of claim 1 wherein said are is positioned in a gap betweenworkpieces and said sensors are directed to preselected spaced areasalong a path within said gap.

4. The method of claim 3 wherein said electrode is a consumableelectrode that is continuously fed to said are and said are influencingparameter is at least one parameter selected from the group of currentamperage, electrode feed rate, and the speed of welding.

5. Continuous electrode welding apparatus comprising:

a. means for continuously supplying consumable electrode wire into anelongated weld zone; b. a sliding electrical current connection to saidwire; c. means for driving said wire and sliding connection over saidelongated weld zone; I

d. sensing means positioned to sense at least two aligned verticallyspaced areas along a preselected welding arc length extending from theconsuming end of said wire to said weld zone, said sensing means beingfurther disposed to signal the existence of said are within each saidspaced area; and

e. means responsive to said sensing means for changing at least one arcinfluencing parameter to bring said are back into the area of detectionof each of said sensing means whenever at least one of said sensingmeans fails to detect the existence of said arc.

6. The apparatus of claim 5 wherein said sensing means consistsessentially of two individual sensing devices synchronized in movementwith said sliding connection, one said device being positioned to sensean area substantially adjacent said weld zone and the other said devicebeing positioned to sense an area substantially adjacent the consumingend of said wire electrode, said means responsive to said sensing meansfor changing at least one arc-influencing parameter consisting of meansdisposed to relatively raise said sliding connection when the sensingdevice positioned to sense an area substantially adjacent said weld zonefails to detect the existence of said are and to relatively lower saidsliding connection when the sensing device positioned to sense an areasubstantially adjacent said consuming electrode fails to detect theexistence of said arc.

7. The apparatus of claim 5 wherein said sensing means consor, saidmeans responsive'to said sensing means for changing at least onearc-influencing parameter consistingof means disposed to lower saidsliding contact when the sensing device positioned to sense an area thatis deeper within. said gapthan the area sensed by the other device failsto detect the existence of an arc and being disposed to raise saidsliding contact when said other sensing device fails to detect theexistence of an arc.

8. The apparatus of claim 7 including means for increasing anddecreasing the speed at which said electrode and said sliding contactpasses over said weld zone, said means being responsive to increase saidspeed when the sensing device positioned to sense an area that is deeperwithin said gap fails to detect the existence of an arc and to decreasesaid speed when said other sensing device fails to detect the existenceof an arc. V

9. The apparatus of claim 7 including means for increasing anddecreasing the feed rate at which said consumable electrode wire is fedto said weld zone, said means being responsive to increase said feedrate when the sensing device positioned to sense an area that is deeperwithin said gap fails to detect the existence of an arc and to decreasesaid feed rate when said other sensing device fails to detect theexistence of an arc.

10. The apparatus of claim 7 including means for increasing anddecreasing both the speed at which said electrode and sliding contactpass over said weld zone and the speed at which said consumableelectrodewire is fed to said weld zone,

. said means being responsive to increase bothsaid speeds when thesensing device positioned to sense an area that is deeper within saidgap fails to detect the existence of an'arc and to decrease, both saidspeeds when said other sensing device fails to detect the existenceot anare.

11. The apparatus of claim 5 wherein said sensing means consistsessentially of two individual sensing devices positioned to sense spacedareas within a weld zone that consists of a gap between adjacent spacedworkpieces, said devices being synchronized in movement with saidsliding contact in a direction parallel with the elongated weld zone,and being spaced from said weld zone, one said device being positionedto sense an area that is deeper within said gap than the area sensed bythe other sensor, said means responsive to said sensing means forchanging at least one arc-influencing parameter consisting of means forincreasing and decreasing the speed at which said electrode and slidingcontact pass over said weld zone, said means being responsive toincrease said speed when the sensing device positioned to sense an areathat is deeper within said gap fails to detect the existence of an arcand to decrease said speed when said other sensing device fails todetect the existence of an arc.

12. The apparatus of claim 5 wherein said sensing means consistsessentially of two individual sensing devices positioned to sense spacedareas within a weld zone that consists of a gap between adjacent spacedworkpieces, said devices being synchronized in movement with saidsliding contact in a direction parallel with the elongated weld zone,,and being spaced from said weld zone, one said device being positionedto sense an area that is deeper within said gap thanthe area sensed bythe other sensor, said means responsive to said sensing means forchanging 'at least one arc-influencing parameter consisting of means forincreasing and decreasing the feed rate at which said consumableelectrode wire is fed to said weld zone, said means being responsive toincrease said feed rate when the sensing device positioned to sense anarea that is deeper within said gap fails to detect the existence of anarc and to decrease said feed rate when said other sensing device failsto detect the existence of an are.

13. The apparatus of claim 11 including means for increasing anddecreasing the feed rate at which said consumable electrode wire is fedto said weld zone, said means being responsive to increase said feedrate when the sensing device positioned to sense an area that is deeperwithin said gap fails to detect the existence of an arc and to decreasesaid feed rate when said other sensing device fails to detect theexistence of an arc.

14. The apparatus of claim wherein said sliding electrical contact ismounted in an electrode holder and said means for changing at least onearc-influencing parameter consists of relatively raising and loweringsaid holder.

15. The apparatus of claim 5 wherein said sensing means each consists ofan elongated housing provided with opposing masks formed with alignedopenings positioned to permit arc light penetration of both saidopenings from preselected areas of said arc, optic fibers aligned withthe opening most remote from said are leading to a photo electric cellthat is disposed to generate an electric current from said are light tosaid means for changing at least one arc-influencing parameter tobringsaid arc back into the area of detection of each of said sensingmeans whenever at least one of said sensing means fails to detect theexistence of said arc, said signal consisting of the interruption ofsaid current.

16. A sensing means for automatically controlling the position of anelectric arc comprisingr a. a pair of spaced sensing means disposed tosense at least two preselected aligned vertically spaced areas along thelength of said electric arc; and b. control means responsive to saidsensing means restoring said are to within the view of both said sensingmeans when one of said sensing means fails to sense said arc.

Dedication 3,602,687.R0be1"t E. Pollock, Hilliard, Ohio. ARC LENGTHCONTROL. Patent dated Aug. 31, 1971. Dedication filed Aug. 2, 1974, bythe assignee, The Battelle Development Gorpomtz'on.

Hereby dedicates to the People of the United States the entire remainingterm of said patent.

[Ofiicz'al Gazette November 12, 1.974.]

1. A method for controlling the vertical position of an arc duringcontinuous arc welding comprising the steps of: a. establishing an arcbetween an electrode and adjacent workpieces and conducting said arcalong a path to effect fusion and welding of said adjacent workpieces;b. positioning at least two aligned vertically spaced sensing means todetect preselected spaced areas along the length of said arc during itstravel along said path, said sensing means being disposed toindividually indicate when they fail to detect the existence of saidarc; and c. changing at least one arc influencing parameter to bringsaid arc back into the area of detection of each of said sensing meanswhenever at least one of said sensing means fails to detect theexistence of said arc.
 2. The method of claim 1 wherein said influencingparameter consists of changing the electric current amperage supplied tosaid arc.
 3. The method of claim 1 wherein said arc is positioned in agap between workpieces and said sensors are directed to preselectedspaced areas along a path within said gap.
 4. The method of claim 3wherein said electrode is a consumable electrode that is continuouslyfed to said arc and said arc influencing parameter is at least oneparameter selected from the group of current amperage, electrode feedrate, and the speed of welding.
 5. Continuous electrode weldingapparatus comprising: a. means for continuously supplying consumableelectrode wire into an elongated weld zone; b. a sliding electricalcurrent connection to said wire; c. means for driving said wire andsliding connection over said elongated weld zone; d. sensing meanspositioned to sense at least two aligned vertically spaced areas along apreselected welding arc length extending from the consuming end of saidwire to said weld zone, said sensing means being further disposed tosignal the existence of said arc within each said spaced area; and e.means responsive to said sensing means for changing at least one arcinfluencing parameter to bring said arc back into the area of detectionof each of said sensing means whenever at least one of said sensingmeans fails to detect the existence of said arc.
 6. The apparatus ofclaim 5 wherein said sensing means consists essentially of twoindividual sensing devices synchronized in movement with said slidingconnection, one said device being positioned to sense an areasubstantially adjacent said weld zone and the other said device beingpositioned to sense an area substantially adjacent the consuming end ofsaid wire electrode, said means responsive to said sensing means forchanging at least one arc-influencing parameter consisting of meansdisposed to relatively raise said sliding connection when the sensingdevice positioned to sense an area substantially adjacent said weld zonefails to detect the existence of said arc and to relatively lower saidsliding connection when the sensing device positioned to sense an areasubstantially adjacent said consuming electrode fails to detect theexistence of said arc.
 7. The apparatus of claim 5 wherein said sensingmeans consists essentially of two individual sensing devices positionedto sense spaced areas within a weld zone that consists of a gap betweenadjacent spaced workpieces, said devices being synchronized in movementwith said sliding connection in a direction parallel with the elongatedweld zone while being spaced relative to said zone, said slidingconnection being capable of independent movement normal to said weldzone, one said device being positioned to sense an area that is deeperwithin said gap than the area sensed by the other sensor, said meansresponsive to said sensing means for changing at least onearc-influencing parameter consisting of means disposed to lower saidsliding contact when the sensing device positioned to sense an area thatis deeper within said gap than the area sensed by the other device failsto detect the existence of an arc and being disposed to raise saidsliding contact when said other sensing device fails to detect theexistence of an arc.
 8. The apparatus of claim 7 including means forincreasing and decreasing the speed at which said electrode and saidsliding contact passes over said weld zone, said means being responsiveto increase said speed when the sensing device positioned to sense anarea that is deeper within said gap fails to detect the existence of anarc and to decrease said speed when said other sensing device fails todetect the existence of an arc.
 9. The apparatus of claim 7 includingmeans for increasing and decreasing the feed rate at which saidconsumable electrode wire is fed to said weld zone, said means beingresponsive to increase said feed rate when the sensing device positionedto sense an area that is deeper within said gap fails to deTect theexistence of an arc and to decrease said feed rate when said othersensing device fails to detect the existence of an arc.
 10. Theapparatus of claim 7 including means for increasing and decreasing boththe speed at which said electrode and sliding contact pass over saidweld zone and the speed at which said consumable electrode wire is fedto said weld zone, said means being responsive to increase both saidspeeds when the sensing device positioned to sense an area that isdeeper within said gap fails to detect the existence of an arc and todecrease both said speeds when said other sensing device fails to detectthe existence of an arc.
 11. The apparatus of claim 5 wherein saidsensing means consists essentially of two individual sensing devicespositioned to sense spaced areas within a weld zone that consists of agap between adjacent spaced workpieces, said devices being synchronizedin movement with said sliding contact in a direction parallel with theelongated weld zone, and being spaced from said weld zone, one saiddevice being positioned to sense an area that is deeper within said gapthan the area sensed by the other sensor, said means responsive to saidsensing means for changing at least one arc-influencing parameterconsisting of means for increasing and decreasing the speed at whichsaid electrode and sliding contact pass over said weld zone, said meansbeing responsive to increase said speed when the sensing devicepositioned to sense an area that is deeper within said gap fails todetect the existence of an arc and to decrease said speed when saidother sensing device fails to detect the existence of an arc.
 12. Theapparatus of claim 5 wherein said sensing means consists essentially oftwo individual sensing devices positioned to sense spaced areas within aweld zone that consists of a gap between adjacent spaced workpieces,said devices being synchronized in movement with said sliding contact ina direction parallel with the elongated weld zone, and being spaced fromsaid weld zone, one said device being positioned to sense an area thatis deeper within said gap than the area sensed by the other sensor, saidmeans responsive to said sensing means for changing at least onearc-influencing parameter consisting of means for increasing anddecreasing the feed rate at which said consumable electrode wire is fedto said weld zone, said means being responsive to increase said feedrate when the sensing device positioned to sense an area that is deeperwithin said gap fails to detect the existence of an arc and to decreasesaid feed rate when said other sensing device fails to detect theexistence of an arc.
 13. The apparatus of claim 11 including means forincreasing and decreasing the feed rate at which said consumableelectrode wire is fed to said weld zone, said means being responsive toincrease said feed rate when the sensing device positioned to sense anarea that is deeper within said gap fails to detect the existence of anarc and to decrease said feed rate when said other sensing device failsto detect the existence of an arc.
 14. The apparatus of claim 5 whereinsaid sliding electrical contact is mounted in an electrode holder andsaid means for changing at least one arc-influencing parameter consistsof relatively raising and lowering said holder.
 15. The apparatus ofclaim 5 wherein said sensing means each consists of an elongated housingprovided with opposing masks formed with aligned openings positioned topermit arc light penetration of both said openings from preselectedareas of said arc, optic fibers aligned with the opening most remotefrom said arc leading to a photo electric cell that is disposed togenerate an electric current from said arc light to said means forchanging at least one arc-influencing parameter to bring said arc backinto the area of detection of each of said sensing means whenever atleast one of said sensing means fails to detect the existence of saidarc, said signal consisting of the interruptIon of said current.
 16. Asensing means for automatically controlling the position of an electricarc comprising: a. a pair of spaced sensing means disposed to sense atleast two preselected aligned vertically spaced areas along the lengthof said electric arc; and b. control means responsive to said sensingmeans restoring said arc to within the view of both said sensing meanswhen one of said sensing means fails to sense said arc.